Tunnel supported on bearing blocks

ABSTRACT

The tunnel supported on bearing blocks is a tunnel to be executed in weak soils, which is constituted by two tubes: an exterior tube, formed by precast elements, which are mounted by a tunnel boring machine, and an interior tube, which is built using the exterior one as the exterior formwork and constitutes the resistant element of the tunnel, both being supported by bearing blocks, regularly spaced along the axis of the tunnel. The bearing blocks are extended downwards until the stiff soil through resistant elements with great horizontal flexibility in order to resist vertical loads, while allowing for horizontal movements of the tunnel during an earthquake.

THE FORMER TECHNIQUE

The execution of tunnels with tunnel boring machines is a solution increasingly used for the construction of infrastructures for roadway and railway transportation systems.

The conventional solution of executing a tunnel with a tunnel boring machine consists of excavating the tunnel with the referred machine, which excavates the soil and places the precast elements which will form the walls of the referred tunnel.

This solution of tunnel building is appropriate for stiff soils, because the tunnels obtained in this way have their stability assured by the strength of the surrounding soil, and so they do not need to have significant strength in both the transversal direction and the direction of the tunnel axis.

In the case of weak soils, the execution of tunnels with a tunnel boring machine is unreliable, because, in the tunnel thus formed, the connections between the precast elements are very weak; hence the strength of the tunnel is low, so it has the risk of sinking, or collapsing, particularly during an earthquake.

TECHNICAL DOMAIN OF THE INVENTION

The present invention constitutes an innovative solution for the construction of tunnels of the roadway and the railway types, executed with tunnel boring machines, when the referred tunnels are executed in weak soils (e.g., mud), which will function as a bridge within the soil. The solution also allows the strengthening of existing tunnels, using the existing tunnel as a formwork for the execution of the interior strengthening.

DESCRIPTION OF THE FIGURES

The present invention is illustrated in FIGS. 1, 2, 3 and 4.

FIG. 1 shows a schematic perspective of the tunnel.

FIG. 2 shows the transversal section of the tunnel and one support.

FIG. 3 shows the longitudinal section of the tunnel and two supports.

FIG. 4 shows the plan of the tunnel and two supports.

DETAILED DESCRIPTION OF THE INVENTION

The tunnel is constituted by two tubes; an exterior tube (3), which is built by the tunnel boring machine in the weak soil, and an interior tube(4), which is executed later on, inside the exterior tube.

The tunnel is supported by bearing blocks (5) executed in the weak soil (1) and regularly spaced along the axis of the tunnel.

The exterior tube (3) is formed by precast elements, which are mounted by the tunnel boring machine, which bores through the bearing blocks (5); it has no resistant function and acts as exterior formwork for the execution of the interior tube.

The interior tube (4) is built inside the exterior tube, using the latter as formwork; the former possesses the necessary strength to resist the transversal and longitudinal actions that may act on the tunnel, without taking into account the strength of the exterior tube(3).

The bearing blocks (5) are extended downwards until the stiff soil (2) through resistant elements with great horizontal flexibility (6), in order to resist vertical loads, while allowing for horizontal movements of the tunnel during an earthquake.

Lisbon, Jan. 10, 2007 

1. (canceled)
 2. (canceled)
 3. Tunnel to be executed in weak soil, being formed by two tubes: an exterior tube which is built by a tunnel boring machine and acts as exterior formwork, and an interior tube, which is cast inside the exterior one with the help of an interior supplementary formwork and possesses the longitudinal and transversal reinforcements of the tunnel.
 4. Tunnel according to claim 3, including disposing of concrete blocks, regularly spaced along the axis of the tunnel, which are extended downwards until the stiff soil through piles with great horizontal flexibility. 